A roller forming machine of the general type to which this invention relates comprises an elongated frame or table on which there are mounted a plurality of forming heads, each comprising a pair of parallel roller shafts that extend transversely to the table. A pair of rollers mounted on the roller shafts of each head have mating profiles and engage opposite sides of an elongated metal workpiece to form it to a configuration in cross section that substantially corresponds to the roller profiles. Successive sets of rollers engage the workpiece to effect progressive modification of its shape until it is worked to a desired cross-section. The roller shafts of each head are rotatably driven in opposite directions so that as the pair of rollers form the workpiece they also cooperate to advance it lengthwise from one forming head to another.
Since a workpiece undergoes a change of cross-section shape at each engagement by cooperating forming rollers, the portion of the workpiece that extends from one such roller pair to another is subjected to a certain amount of stress. In prior roller forming machines, the several forming heads were fixed to the frame at uniformly spaced intervals along it, and it sometimes happened that the fixed distance between a pair of adjacent forming heads was too short for the change in form that would have been imposed upon the workpiece in passing from one to the other of them. In that case it was necessary to remove the rollers from one forming head so that there was a greater length of workpiece between active roller pairs. Often there were two or more forming heads along the length of the frame that were idled in this manner, and frequently, on such occasions, the remaining active forming heads on the machine were too few in number for the required forming operation, so that another complete forming machine had to be used to provide the needed total number of operating forming heads. As a rule, only one or a few of the forming heads on the second machine would be active and the rest would be idle.
What this meant, in practice, was that a shop wanting to be able to handle a variety of roller forming jobs had to have two standard roller forming machines aligned in tandem; whereas the real need was for only one machine with an increased distance between certain of its forming heads and a correspondingly increased frame length.
It was probably apparent that the efficiency and versatility of the roller forming machines could be materially improved if they were provided with forming heads that were adjustable to different positions along the length of the machine frame. But heretofore such adjustability would have given rise to certain problems that had no obvious solution.
The several roller shafts of a roller forming machine should rotate in unison, and for this reason, and as a matter of efficiency, all roller shafts should be driven from a common power source. Drive chains have been used on some roller forming machines, but a chain drive tends toward a jerky or fluctuating torque delivery and is in other respects undesirable in a roller forming machine. The preferred drive mechanism comprises a rotatable power shaft that has gear connections with the roller shafts of the several forming heads. In one common prior arrangement, each forming head carried a short segment of drive shaft that projected forwardly and rearwardly from it, and the shaft segments of adjacent forming heads along the frame were connected by modular lengths of shaft that were key-connected at their opposite ends to the respective shaft segments on the forming heads. To maintain concentricity of the numerous shaft elements, each forming head had bearings in which its shaft segment was journaled, and each modular length of shaft had to extend through a bearing that was carried by a fixed bearing support on the machine frame. Owing to its many bearings, shaft elements and shaft element couplers, such a prior torque transmission system for roller forming machines was not only complicated and expensive but was also, from a practical standpoint, quite inflexible in that it could not readily accommodate adjustable shifting of the forming heads to different locations along the frame.
It can be seen that the provision of a roller forming machine with one or more forming heads positionable at different locations along the length of the machine frame presents the basic problem of providing a simple, inexpensive and versatile mechanism or structure for transmitting torque from a motor to the roller shafts of each such forming head at any location at which the forming head may be positioned.
The present invention contemplates, as a replacement for the heretofore-conventional shaft made up of numerous shaft elements and couplers, a rotatable line shaft which extends along substantially the full length of the machine frame and which consists of one or a few long shaft elements. Rotation of the line shaft is transmitted to the roller shafts on the several forming heads through bevel pinions on the line shaft, one for each forming head, each meshing with a bevel gear on its forming head. With this arrangement, in order for a forming head to be adjustable to different locations along the length of the line shaft, the bevel pinion for that forming head must obviously be correspondingly adjustable along the line shaft. However, such adjustability of the bevel pinions poses problems which will be recognized by those skilled in the art.
Each bevel pinion, at any location at which it may be established, must obviously have a good torque transmitting connection with the line shaft, capable of transferring a substantial amount of power from the line shaft to the driven bevel gear. A keyed connection between the shaft and the bevel pinion is out of the question, not only because of the difficulty in cutting a key slot along substantially the full length of a long shaft but, more important, because the presence of the slot in the rotating shaft would be destructive to any bearing through which the shaft extended. Another consideration that must be kept in mind is that bevel pinions are subject to damage and breakage from time to time, and replacement of a bevel pinion should not require that the long shaft be slid through the damaged bevel pinion and all other pinions and bearings at one axial side of it.
A further complicating factor is that each bevel pinion on the line shaft, in transferring torque to its driven bevel gear, imposes a substantially high lateral force upon the line shaft, and to prevent bowing of the line shaft in response to such force, the shaft should be rigidly supported adjacent to each bevel pinion. The means for affording such support to the line shaft should not interfere with shifting of forming heads from one location to another along the length of that shaft nor with the corresponding shifting of bevel pinions for the respective forming heads.